Folks,
What follows is a general comment and is not related to any specific failure of
an electric VP prop system.
Jos is right to question the quality of the electrics
(motor/switches/diodes/wiring,
etc.) on the Woodcomp SR3000. However, in my opinion, the SR3000 is not
substantially different in quality compared to the other low-cost electric VP
props. In fact, I would rate another low-cost prop as having a far worse
reliability
record than the SR3000 (motor burnouts, intermittent operation, etc.) I
also have experience of yet another manufacturer's products that have exhibited
electrical failures. So although Woodcomp could almost certainly do better,
they are not alone in this regard.
This potential for failure of the propeller system must be acknowledged by the
pilot and they should be mentally prepared for that eventuality. So, whatever
brand of VP prop you have (cheap or expensive), be prepared for it to stop
functioning
at any time.
To reduce the chance of that happening, inspect the prop/hub/wiring regularly.
Ensure that the brushes are in good condition (slip rings clean) and that the
pitch change mechanism operates freely (but not with excessive backlash)
throughout
the normal pitch range.
Most importantly, check that the range of pitch movement is such that the
aircraft
can still fly with the pitch stuck at any position in that range.
With regard to hard pitch stops that come into effect if a switch fails, it
would
be sensible to actually test that the fine pitch hard stop is in a position
that will help save your hide. I suggest that having determined the correct
position
of the electrical switch, measure the static RPM with the pitch on the
limit and then (carefully) override the switch and move the pitch to the hard
limit (use a low voltage perhaps to move the pitch slowly to the stop?) You then
run the engine again and compare the static RPM with the static RPM you achieved
with the pitch on the electrical limit. You can decide on what is an acceptable
rise in RPM. Probably, not much given that the electrical limit was likely
to be set close to the finest position acceptable for safe operation.
Finally, make sure that the pilot (you) fully understands how the pitch is
controlled (controller modes, manual operation, etc.) and what the
appropriate controller settings are for the various flight scenarios.
As part of the pre-flight self-briefing before every flight, acknowledge the
fact
that the pitch may freeze just as you acknowledge the fact that the donkey
may quit at any time.
Regards,
Mark
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